Yes, that sounds about right (I run an FC of 3.5 with CYA of 30ppm or FC of 3.0 when CYA gets down close to 20 ppm) and is the general range I run my indoor pool at. Generally I adjust my CYA to 30 ppm and let it drift down from there to about 20 ppm then boost it back up every 6 months or so. I typically test CYA about every 3 monhts CYA does break down slowly in a chlorinated pool, however this is usually overwhelmed by rain overflow and splash out in an outdoor pool.
I don't recall which test kit you have, but the K-2006 view tube will only read CYA down to 30 ppm, vs the TF-100 which will read down to 20 pppm, but uses much more reagent per test. If you have the TF-100 CYA view tube you can see that the scale is logarithmic and 30 ppm is nearly half way down the tube from the 20 ppm mark.
Of course all of this means avoiding use of stabilized dry chlorine products which will add CYA and just using liquid chlorine / bleach for chlorination.
I don't recall which test kit you have, but the K-2006 view tube will only read CYA down to 30 ppm, vs the TF-100 which will read down to 20 pppm, but uses much more reagent per test. If you have the TF-100 CYA view tube you can see that the scale is logarithmic and 30 ppm is nearly half way down the tube from the 20 ppm mark.
Of course all of this means avoiding use of stabilized dry chlorine products which will add CYA and just using liquid chlorine / bleach for chlorination.
